How to create this painted metal material?
I would suggest to use the Principled BSDF shader, which allows you to create a metallic material with a clear coat. You can add a procedural noise as bump map for the small surface irregularities.

My setup in the screenshot below uses a Musgrave texture, which is connected to the Bump node which in turn is connected to the Clearcoat Normal socket of the Principled BSDF. The Principled BSDF has the Base Color set to nearly black, Metallic to 1.0, Clearcoat to 1.0 as well.